Sprite Animation

1
Sprite Animation

• An exercise on filling circles and polygons to
  create the animated sprite used in Pac Man

2
What is a sprite?

• Its a small graphics pixmap image
• Its normally stored in off-screen VRAM
• Its ready to be copied to on-screen VRAM
• The copying operation is called a BitBlt
• Several sprites can support an animation
• Lets see how to create a sprite array, then
  synchronize BitBlts with Vertical Retrace

3
The Pac Man sprite
1. Fill a circle with the foreground color 2.
Fill a triangle in the background color
4
The Pac Man sprite-array
Create an array of sprites, arranged in a
sequence that matches the order in which they
will be drawn to VRAM
5
Typical animation loop

• sprite pacman 8 // the array of
  sprite-images
• int i 0
• while ( !done )
• draw( pacman i , vramptr )
• vsync() // await next vertical retrace
• hide( sprite i , vramptr )
• i ( i ) 8 // cycle through sprite array

6
Multiple sprite-arrays
RIGHT
DOWN
UP
7
Demo sprites.cpp

• Study the source-code for this demo
• Arrange your sprites in an array
• Write a sprite-animation loop
• Incorporate movement in sprites location
• Let user control direction with arrow-keys
• Store your sprite-arrays in offscreen vram